1. Field of the Invention
The present invention relates to a composition composed of an aqueous solution of L-proline (hereinafter, sometimes simply referred to as “proline”), which is useful as a fertilizer and/or plant vitalizer. In addition, the present invention relates to a method for preserving the aqueous proline solution while avoiding contamination by microorganims. Furthermore, the present invention allows for superior distribution to plants and soil of the novel compositions formulated as commercial products due to their superior preservation.
2. Brief Description of the Related Art
Proline is an amino acid which is known to be effective as a fertilizer or a plant vitalizer (see Japanese Publication No. JP-A 2001-131009). Products containing proline advertising these effects are currently being sold.
To date, proline has been used as a raw material in pharmaceuticals and foods, and therefore is present in a large number of products. However, proline is typically in a crystalline or a powdery state, so it is preserved, distributed, and sold in products as a solid, with almost no moisture content. Among these products, Hanakagami (trade name) (Shoko Co., Ltd.) is a product which contains a high percentage of proline, and which is currently sold in Japan as a fertilizer or a plant vitalizer. Similarly, Hanakagami is preserved, distributed, and sold in a solid powdery state.
Proline products which are preserved, distributed, and sold as solids suffer from caking and deliquescence, due to the high hygroscopic property of proline, which greatly deteriorates the quality of the products. In order to avoid these problems, and to prevent moisture absorption by the proline, conventional solid commercial products are required to include a silica gel having a hygroscopic property stronger than that of the proline, or be packed in a packaging material such as an expensive aluminized film which has almost no moisture permeability.
The main reason proline is distributed as a solid despite the cumbersome burden and cost as described above is that liquid proline solutions easily decomposes and rots from exposure to microorganisms. In other words, many amino acids, including proline, when in aqueous solution without an additive which prevents microbial contamination, such as a preservative or a microbicide, start to gradually decompose due to microbial contamination within several days because of their high nutritive value. This effect is even seen when proline is in a normal preservation environment, but not an aseptic environment. If these problems did not exist, liquid proline is preferable when used in fertilizer or plant vitalizer formulations, because it is excellent in operability and ease of distribution.
Accordingly, there are only a few known methods for preservation and/or distribution, or a proline product useful as a fertilizer or a plant vitalizer, particularly a proline product in a liquid state. Typically, an additive, such as a preservative or a microbicide, is always added to the liquid containing proline in order to prevent microbial contamination.
For instance, Japanese Publication No. JP-B 46-42566 describes that a hydrolysate of proline or of a protein containing proline, an amino acid mixture, or the like is used as the source of proline for a flower-bud formation accelerator which contains a combination of proline and uracil. However, it appears that liquid proline was not used as the raw material in preparation of the flower-bud formation accelerator.
Meanwhile, Japanese Publication No. JP-B 56-32861 describes a solution obtained by decomposing proteins of soybean, a cereal grain, a microbial cell body, or the like by various methods, fermentation solutions of various amino acids, and the like, all of which include proline. However, there is no description about how the proline-containing solutions are preserved and/or distributed.
In addition, Japanese Patent No. 2852677, Japanese Patent No. 2874788, and Japanese Patent No. 2874789 describe an amino acid fermentation solution containing proline, alanine, valine, glutamic acid, and the like, which has been subjected to the removal of cell bodies or sterilization. This solution is intended to apply to plants. However, there is no specific description about how the amino acid-containing solution is preserved and/or distributed.
Japanese Publication No. JP-A 06-80530 describes that an amino acid fermentation solution to be applied to a plant may include an organic or inorganic material in order to facilitate the storage, transport, or handling of the amino acid fermentation solution. That is, it is described that, in order to cover the shortcomings of the amino acid fermentation solution, an organic material or inorganic material of any appropriate kind for improving the preservability or the ability to be distributed is preferably added. Specific examples of the organic or inorganic material include, when it is a liquid, various alcohols, ethers, ketones, aromatic hydrocarbons, paraffinic hydrocarbons, and aldehydes.
Japanese Patent No. 3377873 describes that a solution which is obtained by removing cell bodies from an amino acid fermentation solution containing various amino acids. This solution undergoes a change in the components due to the proliferation of microorganisms if nothing is added to the solution, except when the solution is used immediately. Therefore, it is preferable that the solution be preserved after the pH thereof is adjusted to 3 or less to stabilize the quality. In general, a large amount of a strong mineral acid such as hydrochloric acid or sulfuric acid has to be added in order to adjust the pH of the resulting fermentation solution so that it has a pH around neutral to 3 or less.
Japanese Publication No. JP-A 2001-192310 describes that a surfactant, a pH regulator, or a preservative may be added to an amino acid fermentation solution, as required. Japanese Publication No. JP-A 2002-199812 describes a proline-containing product which contains a surfactant when used in a liquid form. Furthermore, Japanese Publication No. JP-A 2003-48803 describes that proline-containing products can be blended with a microbicide, a surfactant, or a preservative so to prevent spoilage by microbes.